1. Technical Field
The following description relates to an organic light emitting display apparatus usable as a flexible display apparatus and a manufacturing method thereof.
2. Discussion of the Related Art
Recent transition into an information-oriented society has caused rapid development in the field of displays to visually represent electrical information signals, and correspondingly a variety of flat panel display apparatuses exhibiting excellent properties, such as a thin profile, light weight, and low power consumption, have been developed.
Representative examples of these flat panel display apparatuses may include Liquid Crystal Display (LCD), Plasma Display Panel (PDP), Field Emission Display (FED), Electro Luminescence Display (ELD), Electro-Wetting Display (EWD), and organic light emitting display apparatuses.
All of the aforementioned flat panel display apparatuses essentially include a flat display panel to display an image. The flat display panel is fabricated by bonding a pair of substrates to face each other with an inherent light emitting material or a polarizer interposed therebetween. The flat panel display includes a display face defined by a display region and a peripheral non-display region around the display region. The display region is defined by a plurality of pixel areas.
Recently, one kind of flat panel display apparatus, flexible display apparatuses, have been developed, which include a flexible substrate formed of a soft material, thus being capable of maintaining display performance when being bendable like a sheet of paper.
Such flexible display apparatuses may have a broader application range than conventional display apparatuses having no flexibility, and therefore research and development on commercialization of flexible display apparatuses is underway.
Meanwhile, organic light emitting display apparatuses are configured to display an image using self-illuminating organic light emitting devices. That is, the organic light emitting display apparatuses include a plurality of organic light emitting devices corresponding to a plurality of pixel areas.
Typically, such an organic light emitting device includes first and second electrodes arranged to face each other, and an emission layer between the first and second electrodes, the emission layer being formed of an organic material to attain electro-luminescence based on drive current between the first and second electrodes.
The organic emission layer, however, may be easily and rapidly deteriorated due to water, oxygen, and the like. Thus, typical organic light emitting display apparatuses include a sealing structure to prevent invasion of water and oxygen into the organic layer.
FIG. 1 is a partial sectional view of a typical organic light emitting display apparatus.
As shown in FIG. 1, the typical organic light emitting display apparatus 10 includes a thin film transistor array substrate 11, a light emitting array 12 on the thin film transistor array substrate 11, and a sealing structure 13 bonded to the thin film transistor array substrate 11. The thin film transistor array substrate 11 and the sealing structure 13 face each other, with the emitting array 12 interposed therebetween.
The sealing structure 13 includes a sealing layer 13a bonded to face the thin film transistor array substrate 11, a protective layer 13b disposed to cover the top of the light emitting array 12, and a barrier layer 13c disposed between the sealing layer 13a and the protective layer 13b, such that the sealing layer 13a and the protective layer 13b are adhered to each other by the barrier layer 13c. 
The protective layer 13b is a stack of multiple layers formed of organic and inorganic insulating materials having different components or thicknesses. That is, the protective layer 13b includes at least one insulator layer formed of an inorganic insulating material.
However, a thin film formed of an inorganic insulating material tends to transfer the contour of any object thereon. Although a thick film may be contemplated to prevent this problem, this requires disadvantageously high costs and long process time. However, to compensate for impurities on the light emitting array 12, the protective layer 13b, which is disposed on the light emitting array 12, essentially includes an insulator layer formed of an organic insulating material. Formation of a thick organic insulator layer is easier than formation of a thick inorganic insulator layer. This addition of the organic insulator layer, however, is disadvantageous for reduction in the thickness of the display apparatus.
Moreover, the insulator layer formed of an inorganic insulating material is more vulnerable to bending stress than that formed of an organic insulating material. Therefore, the protective layer 13b may easily crack when the flexible display apparatus bends, thus causing generation of impurities.
In addition, because the protective layer 13b and the light emitting array 12 are formed of different materials, separation of the protective layer 13b and the light emitting array 12 may easily occur when the flexible display apparatus is bent.
The cracking, generation of impurities, and separation described above may provide invasion routes for water and oxygen to the light emitting array 12, thus resulting in deterioration in the lifespan and reliability of the apparatus.